The preparation method of an iron-based absorbable implanted medical device comprises cutting or machining a long iron-based absorbable implanted medical device prefabricated tube along the length direction into a plurality of absorbable implanted medical devices having predetermined shapes and lengths (hereinafter referred to as a forming device). The absorbable implanted medical device prefabricated tube can be obtained by drawing a large size iron-based tube blank by a supplier or buying the large size iron-based tube blank from the market and then self drawing by an iron bracket manufacturer, and the cross-sectional dimension and shape of the prefabricated tube are consistent with the cross-sectional dimension and shape of the forming device to be prepared. In order to further improve the mechanical strength of the absorbable implanted medical device, a non-metallic element can be further added into the forming device by a chemical thermal treatment, and the chemical thermal treatment includes, but is not limited to, carburizing, nitriding, and carbon-nitriding. However, the forming device has a very small size and a complex and diverse structure, and is easily deformed under the action of external forces, thus the nitriding charging furnace process of the device has a stringent requirement, a cumbersome charging process, and a low charging amount, resulting in a low nitrification efficiency of the forming device.